Selective signaling and lockout system



April 11, 1944. F. s. ENTZ 2,346,420

SELECTIVE SIGNALING AND LOCK-OUT SYSTEM Filed April 7, 1943 3 Sheets-Sheet l H sur/o/v/ F gal/5r TONE FILTER RAIL WAY ON EITHER FREQ F T127 7 v 20 5 l-m- F1 sua,r1..s'r 3 INVENTOR By E S. ENTZ AT TOkA/FV April 11, 1944. 5 N 2,346,420

SELECTIVE SIGNALING AND LOCK-OUT SYSTEM Filed April 7, 1943 s Sheets-Sheet 2 FIG. 2

STATION 2 CODE A168 g'aw'r TONE FOLAR/ OPE'RA 7T5 ON THE)? FREQ.

Rl/LWAY SELECTOR April 11, 1944. 15, N 2,346,420 SELECTIVE SIGNALING AND LOCK-OUT SYSTEM I Filed April 7. 1943 3 Sheets-Sheet 3 T4 170 3 ODE Ejmr TONE ILTE M /L my La-T OLAR/z OPERA T55 0 min I] FREQ I I I PM in "'H" -l -hlr i 08. TEL,

Patented Apr. 11, 1944 snmorrvn SIGNALING AND LOCKOUT SYSTEM Ferd n nd t E z, M u Ri s. 1 assign t e Te e hone La rat r es, n or or e New York, N a c r ora ion of New York,

Application April 7, 1943, Serial No. 482,095

1 Claim.

This invention relates to selective signaling party line telephone systems arranged to lock out all stations other than the calling and called stations and contemplates the use of two different alternating current frequencies within the Voice range, for example, 600 and 1500 cycles, respectively, alternately applied to a line under control of an impulse transmitter to selectively operate step-by-step circuit controlling devices of the type disclosed in United States Patent 1,343,256 to J. C. Field and commonly referred to as railway train dispatching SB? lectors.

In a specific embodiment of the invention each station on the line is provided with an audio frequency tone oscillator, impulse transmitters of the make and break type and a stepby-step selector of the before-mentioned type whose operation is eifected by causing the oscillator at a calling station to transmit to the line under control of an associated impulse trans; mit e e na e puls f first on quen y and e ther, hen h p n ntacts of the transmitter are closed one frequency (600 cycles) is generated and applied to the line and when the contacts are opened the tuning of the oscillator is changed so that it generates another frequency (1500 cycles).

This alternate changing of the line frequency back and forth between 600 and 1500 cycles in accordance with predetermined codes is translated to all the stations other than the calling station, into direct current impulses which cause the selectors thereat to advance in the manner previously described in the Field Patent 1,343,256, which selectors, depending on the setting thereof as determined by the code transmitted, control circuit means to prevent (i. e., lock out) the subscribers at such station from gaining access to the line, to selectively signal and unlock the called station to the exclusion of the others or to remove the look-out condition at a ati ns.

The invention will be best understood from the following description of the system which is shown on the accompanying drawings Figs 1, 2 and 3 which represent three stations 1, 2 and 3 on a line L whose individual or selective codes are 1359, 1363 and 1377.

Let it be assumed that the line is idle and that station 1 desires to communicate with station 3, with which line is also associated other stations, one of which, station 2, is also shown. To originate a call, the subscriber at station 1 removes his receiver R1 from the hook, thereby closingcontact I of his switchhook to operate relay 2 over conductors 3, 4, 5, 6 and contacts I, 8 of relay 9. Relay 2, in operating, closes a circuit to operate the telephone connecting relay IO which can be traced from battery, contact of relay 2, winding of relay i0, contact H of relay l2, contact 13 of the release relay [4, and lower contacts of ringing relay 9 to ground. Relay 10, in operating, closes its contacts l5, l8 thereby connecting the telephone T1 to the line L in an obvious manner. The subscriber at station 1 then operates the dial key l1 associated with his telephone thereby closing its contacts 18 to light the filaments of the vacuum tubes of the oscillator OSC]. thereat which starts to generate a frequency within the voice range (600 cycles) in a well-known manner which generated frequency passes to the line L over contacts l9 and 23 of key IT, transformer 2|, conductors 5 and 6, contacts. I and 3 of relay 9', transformer 2-2, and contacts t5, It of relay Hi. If the calling subscriber desires to com,- municate secretly with the subscriber at station 3. to the exclusion of station 2 and any others on the line, he operates the pulse transmitting device L01 which in returning to normal, in a well-known manner, alternately opens and closes its contacts twenty-one times, thereby alternately changing the tuning of OSC1 between its normal frequency of 600 cycles and 1500 cycles, which latter frequency is produced when the short-circuit around condenser 23 is removed.

When the 600 cycles was first connected to the line it was received at all the other stations, station 3, for example, amplified by amplifier A3 and passed into the 600-cycle filter Fa where it was passed out over conductors 24 and 25' to the rectifier bridge 26 and translatedinto direct current and applied to the upper winding of polar relay 2! over contacts 28 of relay 23, thus causing the relay 2] to operate and move its armature into contact with its grounded righthand contacts, thus causing the charged condenser 30 to discharge through the winding of selector 3| and move it one step and immediately drop back to normal where it remains as long as the 600 cycles remains on the line. When the lock-out key L01 at station 1 is operated, and starts to return to normal, the first open pulse removes the short-circuit from condenser 23 of the oscillator which changes the frequency thereof to 1500 cycles which passes over the line to the filter F3 and out over leads 24 and 32 'to the rectifier bridge 33 where it is also trans on its seventeenth contact. this is accomplished forms no part of the invenlated to direct current and applied to the middle winding of relay 2! in a direction to move its armature to the left in contact with battery instead of ground, thereby causing a charging current to flow through condenser 30 and selector 3| to again cause the selector to take a step.

It will be noted that regardless of the direction in which the armature of relay 21 is moved, the bias current in its lower winding is always in a direction to hold it in the position to which it was moved by either its upper or middle winding. It will also be noted that both the upper and middle windings of relay 34 are normally short-circuited at the back contacts of relay 29.

As the locking key L01 continues to transmit alternate pulses of 600 and 1500 cycles, relay 2'! will move its armature back and forth between its contacts to cause the selector 3| to step ahead and at the end of the twenty-one pulses it will rest at its twenty-first step and remain there by well-known means as described in the Field patent previously referred to.

Movement of the selector 3| to its twenty-first terminal closes a circuit from ground to energize lock-out relay 35 which looks over its lower winding and contact 36 to ground at the lowermost contacts of ringing relay 31. As all selectors connected to the lines move in synchronism and stop on contacts 2| the lock-out relay of station 2 which corresponds to relay 35 of station 3 will be operated.

Operation of relay 35, and all other corresponding relays at the other station, opens its contacts 39, thereby preventing all relays corresponding to relay l at station 1 (such as 49 and 53) from operating and connecting the associated telephones with the line in case the subscriber removes his receiver from the hook. Also the operation of all relays, such as 35 and 5|, close their lowermost inner contacts, such as 41, thereby operating relays, such as 48 and 50, over their left-hand winding, which relays, in operating, close at their right contacts a circuit to apply another direct current pulse to the associated selector, such as 3|, at thatstation which is effective to restore it to normal, in the usual manner.

The calling subscriber at station I, after having locked out all stations by transmitting the twenty-one lock-out pulses proceeds to transmit, by means of the dial D1, the desired subscriber's code which we have assumed is 1377. In this case the first digit 1 is common to all the other codes of the line and is for the purpose of releasing any selectors which may not have released when the lock-out relay, such as 35, operates, as above described, or in case one or more of the selectors becomes advanced and locked by voice currents which may be present on the line between the time the look-out pulses are transmitted and the station code dialing commences. The remaining three digits 377 when added together total 17 and when transmitted, one digit at a time, only the selector 3| at station 3 will reach and hold The means whereby tion and is disclosed in the previously mentioned Field patent.

When the first digit 1 of the code is transmitted, the line frequency is changed momentarily from 600 to 1500 cycles, thereby momentarily energizing all the selectors which release, if they have not already done so, and return to normal,

but it will be noted that relay 35 which was operated at the end of the twenty-one lock-out pulses remains looked under control of relay 3'! and consequently does not release at this time. The next three digits transmitted, i. e., 377, which are characteristic of station 3 only, advance selector 3| at that station to its seventeenth terminal where it locks in the well-known manner but the selectors at all other stations, not being adjusted to this code, drop back at the end of each digit and hence do not reach their seventeenth terminal. When selector 3| stops on terminal I! it closes a circuit to operate the ringing relay 31 which opens its lowermost contacts, thereby removing the locking ground of relay 35, which relay releases, thus removing, at its upper contacts, the busy tone from the left Winding of the repeating coil 38 and at its contacts 41 also releases relay 48. Relay 35, in releasing, also recloses its contacts 39, thereby placing relay 40 in conditions for operation when the telephone receiver at this station is removed from the hook. Relay 3! also closes its inner alternate contacts, thus connecting ringing current to conductors 4| and 42 extending to the telephone set T3 to actuate the ringer 43 thereat. Operation of relay 3'! also closes its contacts 45, thereby operating relay 29 which opens its contacts 28 and 46 which remove the short-circuits around the upper and middle windings of relay 34 which relay operates to move its armature to the left due to the frequency present on the line. Operation of relay 34 energizes slow-release relay 48 again, now over its right Winding, to prepare a circuit to give the selector a release impulse when the dial key at the calling station is released.

When the calling subscriber concludes dialing the code of the called station, he releases dial key thereby stopping and disconnecting the oscillator; thereby permitting relay 34 of the called station to move its armature to the right under the influence of its lower or bias winding, thereby opening the circuit of the right winding of relay 48, but before this relay which is slow to release breaks its contacts the right-hand contact of relay 34 makes, thereby causing a momentary impulse to be transmitted to the selector 3| which releases as before mentioned. When the selector restores, the circuit of ringing relay 3! is opened and the bell at the called station is silenced. When the called subscriber removes his receiver from the switch-hook, relay 44 operates, thereby connecting the telephone set through to the line by operating relay 40, whereupon conversation between the calling and called parties takes place to the exclusion of all the other stations which are locked out.

At the conclusion of the conversation the calling, or called station, actuates the respective dial key, such as ll, thereby energizing the oscillator. He then actuates the release pulse transmitter, such as RLS1, thereby sending twenty-three pulses to the line which steps all the selectors to the twenty-third terminal whereupon an associated release relay, such as 49 at the locked-out station 2, operates to close its right-hand contacts, thus again operating relays, such as 59, to apply a single current impulse to the selector thereat to cause its release. Relay 49, in operating, also opens its left-hand contacts to open the-holding circuit for the lock-out relay, such as 5|, which releases and closes its contacts, thus conditioning the telephone connecting relay 53 for operation whenever its associated telephone set is taken for use. When the dial key is released the sys.

response to another code, and each device being adapted to take still another setting in response to a predetermined individual code, a telephone set including a signal device at each station, means responsive to taking any one of said telephone sets for use to connect it to the line, means at all stations responsive to a said first common setting of the switching device thereat to disable the associated connecting means, other means at each station responsive to an individual predetermined setting of the switching device to enable the line connecting means at that station, and still other means responsive to said second common setting of said switching device to enable the connecting means thereat, if disabled.

' FERDINAND S. ENTZ. 

